1. Technical Field
The present invention relates to a duct molded from a thermoplastic resin.
2. Background Art
The following methods are methods of molding a duct, which is an example of a resin molded product. Two pre-molded sheets are reheated and placed in a molten state between a pair of upper and lower molds. After this, a pressurized liquid is blown in between the two sheets, while closing and adjusting the pair of molds. Consequently, a climate control duct is formed in which the first half and the second half are joined as a single unit.
Furthermore, for example, a sheet blow molding method using a foamed resin sheet is disclosed in JP-A-2001-239824 (Patent Document 1) and JP-A-2000-289093 (Patent Document 2).
In the sheet blow molding method, two thermoplastic resin sheets cut in a predetermined size in advance are heated with an infrared heater and softened. Next, the sheet is pinched-off from the mold. Then, the sheet is attached firmly to the surface of the cavity by the blowing of a pressurized fluid between the sheets. Due to this, the sheet is molded into the desired shape.
However, in the sheet blow molding method mentioned above, sheets prepared in advance in room temperature are softened during sheet blow molding by reheating it with radiant heat sources such as infrared heaters. Therefore, for example, when foamed resin sheets are used, it is difficult for the sheet to be in a uniform molten state including its internal mass. In addition to this, when compared with molten and extruded sheets, the reheated sheets contain less heat. Therefore, not only does this cause poor traceability for the sheet along the mold's cavity, but also inadequate adhesion at each pinched-off section (parting line) of the two sheets.
Furthermore, WO 2009/157197 (Patent Document 3) is an example of the related art by the present applicant. A molding apparatus of molding a resin molded product using a molten thermoplastic resin sheet is disclosed in this document.
Patent Document 3 mentioned above discloses the molding of plate-shaped resin molded product, such as sandwiched panels, using molten thermoplastic resin sheets. However, in this document, no reference is made regarding the molding of a duct.